Hydraulic pump



oct. 2o, 1942. J, SNADER ETAL 2,299,235

HYDRAULICUMP 2 Sheets-Sheet 2 Original Filed June 9, 1937 @25 K? 86 I W6 d@ mm @fw mi Odvmij Patented Oct. 2o, 1942 HYDRAULIC PUMP Ira J. Snader and Max A. Mathys, Detroit, Mich., assignors to Ex-'Cell-O Corporation, Detroit, Mich., a corporation of Michigan original application June 9, 1937, serial No.'

147,178. Divided and this application July 31, 1940,4 serial No. 348,904

(Cl. S- 162) 12 Claims.

pressure operation.

One object of the invention is to provide a novel hydraulic pump which is silent in operation at high pressures, and in which the mechanical reaction of the hydraulic pressure on the wearing surfaces is hydraulically balanced.

Another object is to provide a new and improved pump valve which'will not deflect under high pressures, and which is constructed to prevent sudden pressure changes in the pump cylinders with resultant pressure surges in the delivery.-

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is an axial sectionallview, taken along line I-I of Fig. 2, of a pump embodying the features of our invention.

Fig. 2 is an end elevational view of the pump.

Fig. 3 is a fragmentary sectional view of the pump valve taken along line 3-3 of Fig. l.

Fig. 4 is a fragmentary transverse sectional view taken substantially along line 4-4 of Fig. 1, and showing the face of the stationary valve member.

has a bottom wall I4 adapted to be bolted or otherwise secured to a suitable support (not shown). The housing I3 also has opposite end walls I5 and I6, and is closed at the top by a removable cover plate Il.

A suitable drive shaft I8 extends longitudinally through the housing I3, and is journaied at opposite ends in the walls I5 and I6. Integral with the wall I5 is a large external circular boss I9 having an axial bore 2li counterbored at the innerend. A stationary vlalVe plug 2I, in the form of a single cylindrical block, is tightly pressed into the bore 20, and is located axially by a peripheral end flange 22 seated in the counterbore. To locate the plug 2I angularly. it is formed-with a longitudinal groove 23 engaging a pin 24 on the inner end'of a screw 25 threaded radially into the boss I9. Formed in the plug 2| is an axial bore 26 which is closed at the Fig. 5 is a fragmentary transverse sectional v view taken substantially along line 5-5 of Fig. 1,

and showing the face of the movable valve member.

Fig. 6 is a sectional detail view taken along line 6 3 of Fig. 4.

Fig. 7 is an enlarged fragmentary sectional view of one of the pump pistons.

While the invention is susceptible of various modifications and alternative constructions, we have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that we do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions failing within the spirit and scope of the invention as expressed in the appended claims.y

The present application is a division of our copending application Serial No. 147,178, iiled June 9, 1937.

ljteferring more particularly to the drawings, the hydraulic pump, constituting the exemplary embodiment of the invention, comprises a closed pump housing VI3 which may be of any suitable form or construction, andwhich in the present instance is generally rectangular in shape, `and shown).

other foreign matter through the bearing 23' into the housing I3, an oil seal 30 is mounted in the outer end of the bore 28, and is held in place by an end plate 3I bolted to the outside of the wall I6.

Secured to the-shaft I8 for rotation therewith is a cylinder block or body 32. In the present instance, the body 32 is formed with an axial bore 33 slidably receiving the shaft I8, and is located axially thereon -by abutment against a shaft enlargement 34. 'The end of the enlargement 34 is attened onvopposite sides'to define a key 35 which interflts separably with a diametrical notch 36 in the adjacent end of the body 32. Preferably, the root of the notch 36 and the end face of the key 35 are arcuate in shape to provide simple machining.

The body 32 is in the form of a spool having a peripheral cylinder flange 3l and an axially spaced guide flange 38, and defining an intermediate spring space 39. A plurality of parallel bores 40,' six in the present instance, open through the ange 31, and constitute pump cylinders an- -nularly arranged inv uniformly spaced relation about the shaft I8. Similarly, the flange 38 is formedv with guide bores 4I in axial alignment with 'the'bores or cylinders 40. Rigidly secured as by means of bolts 42 tov the outer end face of the ange .31 and coexterisive in diameter therewith is a circular valve plate 43 which closes the pressure ends of the cylinders 40, and which preferably is formed with circular recesses defin ing rslightly enlarged closed end extensions of the cylinders. g

A plurality of pump plungers' or pistons 44 are reciprocably disposed respectively in the open ends of the cylinders 40 and are slidably guidedv sequence, with a variable stroke as hereinafterv described, by asswash or cam plates 49 which is journaled on a pin 59 for angular or rocking adjustment into differentinclined positions. The

pin 50 is pressed in spaced lugs 5I inthe housing.l I3 and is perpendicular to the axis of the shaft I8. The plate 49 has a flat annular cam face 52 which freely encircles the shaft enlargement 34 and which is engaged by floating shoes 53 operatively connected to the outer ends of the pistons 44.

Each of the shoes 53 is in the form of a.disk having a fiat annular bearing face 54 of ample size in sliding engagement with the cam face 52, and having a hollow central spherical projection 55 seating for universal movement in a complemental socket 55 in the outer end of the associated piston 44. A retainer 57 is loosely fitted in the outer end of an axial bore 58 in the piston 44, and is secured therein by a transverse lock pin or rivet 59. The retainer l has a semispherical head 6U which engages the interior of the projection 55 to confine the shoe 53 adjustably in the socket 55, and which is connected by a reduced stem 6l extending freely s through a centralopening 62 in the projection.

The bore 58 opensat the -inner end through a small aperture 63 to the cylinder 40, and hence provides for a longitudinal pressure passage permitting the fiow of lubricant to the bearing surfaces of the shoe 53. As one factor affecting quietness in pump operation, the lubricant passage should be small. Since it is impracticable toV drill the long bore 58 sufliciently small in hard metal, suchv as the piston material, a seamless tube 64 is tightly fitted therein between the retainer 5l and the aperture 63, and defines the actual pressure passage.' Fluid or oil from the closed end of the cylinder 40 passes through the aperture 53, the tube 64 and about the retainer 5l to the bearing surfaces of the socket 59 and ball projection 55. Fluid or oil also passes through the opening 62 to the-bearing surfaces between the plate 49 and the shoe 53.

The bearing surfaces between the plate 49 and the shoe 53 andv between the projection 55 and the socket 55 are closely lappedto provide a hydraulic seal, and are hydraulically balanced against the mechanical reaction on the piston to outward thrust of thejhydraulic pressure in the a concentric drain groove 95 relieved through a plurality of drain apertures 67. The central portion of the bearing face 54, crcumscribed by the inner edge of the `groove 56, is under pressure. and is substantially equal in area to the pressure end of the piston 44 so as to counterbalance the cylinder 49. The pressure area of theface 54 may be equal to the piston end area, but preferably is slightlyv larger to balance part of the outward pressure of the spring 45. Since the groove 5B prevents outward spreading of the pres- I sure film, the full wearing surface of the face 54 can be muchv larger than the pressure balanced areawithout interfering at any time with good bearing contact. The effective pressure area of Athe socket 56 is somewhat less by reason of the opening 52 than that 'of the piston 44, but is sufciently large to obtain substantially a hydraulic balance, the lubricating film being maintained under a slight excess pressure to assure good bearing contact. y

' The valve stator 2| and the plate 43 have annular end faces 68 and' 69 in bearing engagement, and constitute a rotary'end face valve for controlling the admission and discharge of fluid Since respectively to and from the pump units. the stator 2l is in the form of a heavy plug mounted in the large boss I9, the stationary valve face 68 is not subject to deflection under heavy pressure.

The valve stator 2| (see Fig. 4) is provided with two arcuate suction and delivery ports 'l0 and 'li separated by diametrically spaced land areas I2`and I3 and arranged in concentric relation to the shaft I8. These ports are located at opposite sides of an axial plane intersecting the land areas and perpendicular to the pivotal axis of the swash plate 49. Formed in the valve face 69 of the plate 43 are a plurality of ports 'i4 which open respectively to the closed ends of the pump cylinders. 40, and which are annuadjacent the shaft I8. As a result, the contactrotation to reduce the peripheral speed. Also,

any air collecting in the cylinders 40 will be separated from the liquid by centrifugal force, and pass out with the pump delivery.

The valve faces 68 and 69 are hydraulically balanced against the pressure in the minimum number of cylinders 40 on the pressure side oi the pump to maintain a proper oil film and good contact. Since the cylinders under pressure are alternately two and three, the area of the valve face 58 on the pressure side, including the port ll, is made substantially equal to the aggregate area of the ends of two pistons 44. To obtain a bearing surface larger than the balancing pressure area, an annular concentric drain groove 'I5 is formed in the face 68 about the ports 'I0 and 1I to prevent spreading of the pressure film, and is relieved at spaced points to the periphery of the plug 2|. The inner peripheral edge ofthe valve face 58 is relieved to the bore 26, and the liquid draining from the valve faces into the bore serves to lubricatethe bushing 21. Liquid co1- lecting in the bore 26 at opposite ends of the bushing 21 is free to pass through drain holes I6 and II to the locating spline groove 23, and from there into the housing I3. Liquid collecting in the housing I3 is free to return through a passage 'I8 to the pump inlet. If the pump is mounted above the level of the source of liquid supply, the passage 'I8 may be closed, and the housing I3 may be drained through a bottom opening 'I9 connected to the source.

It will be evident that wl en the swash plate 49 is angularly disposed, rot...tion of the cylinder body 32 will cause the pistons 44 to be reciprocated in timed sequence and with a simpleharmonic motion, and that each piston will be moving through its suction and pressure strokes while the associated cylinder 40 is in communication respectively with the inlet and delivery ports I and 1I. As the pistons 44 of each set of diametrically opposed pistons reach top and bottom dead centers respectively, the associated cylinders will be closed by the land areas 'I2 and "I3, and at these times only two cylinders will be open to either of the valve ports IU and 1I. At

all other times, three cylindersH 40 will be open i to each of the valve ports I0 and 1I. Consequently, the pump will discharge continuously, and the rate Yof discharge is substantially constant for any given setting of the swash plate 49.

Ifthe angular position of the swa'sh plate 49 is changed, the length of the piston stroke will be adjusted to adjust the rate and volume ofpump delivery. When the plate 49 is adjusted into a plane lperpendicular to the shaft I8', no reciprocation will be imparted to the pistons 44l Preferably, the suction and delivery ports I0 and II are angularly advanced in relation to the top and bottom dead center positions of the pistons 44 so as to effect a pressure equalization in each cylinder 40 just before the start of both the pressure and suction strokes.4 Each of the cylinder ports I4 will be closed by the land area 'I2 during the initial part of the pressure stroke l to cause the pressure therein to be built up approximately to the pump delivery pressure be.- fore free communication with the port 1I. Similarly, each port I4 will be closed by `the land area 'I3 during the initial part of the suction stroke so that the pressure will be expanded approximately to the suction pressure effective in the port 'I before free communication therewith.

To permit such pressure equalization, the land areas I2 and 'I3 are somewhat wider than the ports 'I4 so that each cylinder 40 is closed over a predetermined degree of revolution. For fixed operating conditions and upon making proper allowance for leakage past the valve faces and,

pistons, the angular advance of the ports 'I0 ,and 'Il may be accurately calculated to obtain a quietly operating pump. However,the operating conditions are subject to variations, such, for example, as changes in delivery pressure, speed, displacement, temperature influences and the kind and condition of the uid being handled. 'I'hese changes influence'the pump leakage and the pressure gradients, The'valve ports 10 and ing to and constituting extensions of the ends of the arcuate ports 10 and 1I. The grooves are so graduated that the cylinder ports 'I4 will not open abruptly to the ports 'I0 and "II, thereby avoiding sudden shock even if the cylinder pressure is not equalized with that of the stationary port with which it is about to communicate.

The gradual pressure changes in passing from either to the other of the ports' I0 and 'II also have the important function of preventing the piston shoes 53 from clicking, During movement through the intake zone, each shoe 53 is held against the cam plate 49 with a light initial presszu'e determined by the spring 45. In the pressure zone, the spring pressure is supplemented by the hydraulic pressure acting through the piston 44 so that the oil film between the cam plate 49 and the shoe 53 and between the latter and tie piston is compressed under a heavy pressure. By reason ,of the advance of the ports I0 and Hand/or the provision of the bleed grooves 89, the pressure on the film is 'alternately gradually relieved and applied, thereby placing the shoe 53A in substantial balance before each port opening. Sudden pressure surges tending to effect separation of the shoe 53 from the cam plate 49 at transition points in the operation are consequently avoided.

As noted, one of the features cf the present pump is quietness in operation. The hydraulic baance of the piston shoes 53 and the valve 68, G9 against the mechanical reaction of the hydraulic pressure contributes to this result. The elimination of pressure surges or impulses, by reason of the angular advance cf the ports 'III and 'II and the provision of the bleed grooves 18, also reduces noiseI in operation. Asanother important factor in avoiding noise, the volume fof pressure liquid 'in the clcsed ends of the cylinders 4!) at the end of the pressure stroke is held to a minimum. To this end, the piston clearancein the valve plate 43 is made as small as is practically convenient, and the pressure passages through the pistons 44 are reduced in Y stroke.

, while the outward limit of movement is variable 1I are therefore advanced to time the opening 38 in the valve face 68 (see Figs. 4 and 6) open- 75 in accordance with changes in the angular .position of the swash plate 49.

The inlet portfIII may be connected in any suitable manner to the source of liquid supply, and in the present instance is in communication at the bottom or root with a plurality of longitudinal bores 8|l in the valve plug 2l, The outer ends ofthe bores 8I are intersected by a recess 82 formed in the periphery of the plig, and registering with a passage 83 opening through the f .peripheral wall of the boss I9. A line 84 connect-s the passage 83 with. a source of supply, such as asump or-reservoir 85. The delivery port 1I is in communication at the bottom or rootywith `a -plurality of longitudinal bores 86 formed in the plug 2I. A recess 31 in the periphery ofthe plug 2l intersects the bores 86, and is in registration with an out-let passage 88 opening through the bess I9 and conne-:ted to a pressure line 89.4

The swivel plate 49 may be angularly adjusted about the pin 5I to vary the output of the pump. Within the broad aspects of the present invention,

' such adjustment may be effected by any 'suitable'means. -In the present instance, the swivel.

Thus, the

ends .of .said cylinders, and contacting with said stationary valve face for movement o f said cylinder ports successively across said intake and delivery ports, a plurality of pistons reciprocable in said cylinders, and means for effecting reciprocation of said pistons in timed sequence, said pose comprises a control piston 90 acting on the free end of the swash plate 49 in a direction to level oi the latter against the hydraulic reaction in the cylinders 49 `and the action of the piston return springs 45. 1 The control piston 99 is reciprocable in a cylinder 9| opening through the wall I6, and closed at the outer end by the cover or stop plate 3 I. The cylinder 9| extends parallel to the 'shaft I8, and preferably is located diametrically opposite the pin 50 and outside the circle of revolution of the cylinders 49 so that the lthrust of the piston 90 against the plate 49 will have a moment-` arm considerably longer than that of the aggregate opposing forces resulting i from the hydraulic reaction through the pistons 44. The diameter of the piston 99 and the moment arm of the force exerted thereby detercorresponding pump delivery pressure.

The control piston 99 is operatively connected to the swash plate 49 by a pin 92. One end of the pin 92 is formed with a spherical head 93 seated for universal pivotal movement in a complemental socket 94 in the free end of the plate 49, andthe other endis rounded and seatedin a complementalsocket 95 in the end wall of the piston 90. A coiled compression spring 96 acts to maintain the head 93 within the socket '94.

Fluid under pressure is adapted to be'supplied to or exhausted from the inner end of the cylinder 9| to adjust the swash plate 49. In the present instance, the supply of iiuid is controlled by a metering valve 91 which preferably is built into the coverv I1 and which is automatically responsive to the aforesaid control pressure. The details of the valve 97 and the source of the aforesaid control pressure form no part of the present invention and are thereforenot specifically illus- 'of said casing, a cylindrical plug tightly itted in said bore and having 'an inner end ange engaging the inside of said wall, spline means for locating said plug angularly vof said bore, the inner end'of said plug defining a fiat stationary valve face with arcuate intake and delivery ports in communication through said plug respectively with 'said passage means; an axial bore in said plug centrally of saidports and draining from `opposite ends to the interior of said casing, a

drive shaft in said casing and journaled at one end in said last mentioned bore, a pump body xed to said shaft and having a plurality of parallel pump cylinders annularly -arranged about K- said shaft, a valve face on one end of said body having ports openingI respectively tothe closed plug being of suflicient mass to prevent deflection of said stationary valve-face under pump presy sure.

2. A hydraulic pump comprising, in combination, a casing having a bore in one wall, a unitary plug of substantial mass tightly fixed lin said bore and defining a stationary valve face at the inner end, a drive shaft in said casing, a pump body fixed on said shaft and having a plurality of parallel pump cylinders annularly arranged about the the axis of rotation, a valve face on one end of said body and contacting with said stationary valve face, a plurality of pistons reciprocable in said cylinders, and means for effecting reciprocation of said pistons in timed sequence, said mass being suicient to prevent appreciable deflection of said stationary valve'face under pump pressure. l

' 3. A hydraulic pump comprising, in combination, a pump casing having fluid inlet passage means and pressure delivery passage means, a shaft journaled in said casing, a pump body secured to said shaft for rotation and having a plurality of parallel cylinders annularly arrangedv about said shaft, a plurality of pistons reciprocable in said cylinders, valve means for connecting said cylinders alternately and successively to said inlet and delivery passage means respectively during the intake and pressure strokesof said pistons, a swash plate mounted in `said casing for reciprocating said pistons in timed sequence upon rotation of said body, lsaid swash plate having a fiat bearing face, each piston having a floating shoe at the outer end with a bearing face slidably engaging said flat bearing face of `said swash plate and being hydraulically balanced against the mechanical reaction of the pressure in the associated cylinder.

'4. A hydraulic pump comprising, in combination, a casing having uid inlet passage means and pressure delivery passage means, a shaft journaled in said casing, a pump body rotatable with said shaft and having a plurality of parallel cylinders annularly arranged about said shaft and .having ay plurality of guide bores in axial alignment -with saidl cylinders, a plurality of pistons reciprocable in said cylinders. and said guide bores, valve means for connecting said cylinders alternately and successively to said inlet and delivery -passage means respectively during the intake and pressure strokes of said pistons, a swash plate adapted to be mounted in inclined position relative to a perpendicular to saidshaft for reciprocating said `pistons in timed sequence, and individual compression springs encircling vsaid pistons between `said cylinders and guide bores and urging said pistons outwardly into operative engagement with said swash plate.

5. A hydraulicpump comprising, in combination, Aapump casing having fluid inlet passage means and pressure delivery passage means, a rotatable pumpbody having a plurality'of'parallel cylinders-annularly arranged about the 'axis of rotation,` a plurality of pistons reciprocabl in saidcylinders, means for effecting reciprocatibn of said pistons in timed sequence',A and valve means for connecting said cylinders alternately and successively to said inlet and delivery passage means, said valve means comprising a staber of cylinders adapted to be under pressure at one time. l

6. A hydraulic pump comprising, in'combination, a pump casing having fluid inlet passage means and pressure delivery passage means, a

pump body having a plurality of parallel annu-` larly arranged cylinders, a plurality of pistons reciprocable in said cylinders, means for effecting reciprocation of said pistons in timed sequence, and end face valve means for connecting said cylinders alternately and successively to said inlet and delivery passage means, said valve means comprising contacting valve faces having means for defining a pressure lm area substantially equal on the pressure side of the-pump to the aggregate area of the minimum number of cylinders adapted to be under pressure at one time. v

'7. A hydraulic pump comprising, in combination, a pump casing having fluid inlet passage means and pressure delivery passage means, a rotatable pump body having a plurality of parallel cylinders annularly arranged about the axis of rotation, a plurality of pistons reciprocable in said cylinders, means for eiecting reciprocation of said pistons in timed sequence. and valve means for connecting said cylinders alternatelyy and successively to -said inlet and delivery passage means, said valve means comprising a stationary valve face, and means in said face defininga pressure film area of a size adapted substantially to balance hydraulically the mechanical reaction of the hydraulic pressure on saidA valve means while maintaining a. hydraulic seal.

8. In a hydraulic pump, in combination, a pump bodyhaving a cylinder, a piston reciprocable in said cylinder, an inclined swash plate operatively engaging the outer end ofv said cylinder, means for effecting relative rotation between said body and said swash plate,` valve means for admitting uid to said cylinder and delivering pressure iluid therefrom respectively during the intake and delivery strokes of said piston, said piston being formed with an axial bore opening through a restricted aperture to said cylinder, a tube fitted into said bore to reduce the size of the passage therethrough, a spherical socket in th outer end of said piston, a shoe having a ilat annular bearing face in slidable engagement with said swash plate and having a central rounded projection seating for universal adjustment in said socket, a retainer loosely secured in the outer end of said bore and having a head coactilning said shoe in engagement with said socket, whereby fluid from said cylinder passing through said aperture and said tube vis available to lubricate the contact surfaces between said socket and projection and between said swash plate and shoe, an annularv groove formed in the bearing face of said shoe and relieved to the atmosphere to define a circumscribed pressure area lessl than the total area of said bearing face and approximately equal to the end area of said piston to meer a hydraulic mance of said shoe aainst the mechanical reaction to the pressure in said cylinder.

loy

'ing with the inside of said projection for con- 9. In a hydraulic pump. in combination, a pump body having a cylinder, a piston reciprocable in said cylinder, an inclined swash-plate .having a ilat bearing face operatively engaging the outer end of said piston, means for effecting relative rotation between said body and said swash plate, l

valve means for admitting fluid to said cylinder and delivering pressure fluid therefrom respectively during the intake and delivery strokes of said piston, said piston being formed with a bearingsocket in the outer end and with a longitudinal passage opening from said cylinder to said socket, a shoe having a flat annular bearing face in slidable engagement with said bearing face of said swash plate and having a central projection seating for angular adjustment in said socket, and an opening in said shoe for connecting said passage to said bearing face.v

l0. In a hydraulic pump, -in combination, a

pump body having a cylinder, a. piston reciproca'ble in said cylinder, an inclined swash plate operatively engaging the outer end of said cylinder, means for effecting relative rotation between said body and said swash plate, valve means for admitting fluid to said cylinder and delivering pressure fluid therefrom respectively during theintake and delivery strokes of said piston, said pistony being formed with a bearing socket in the outer end and with a longitudinal passage opening from said cylinder to said socket, a shoe having a flat bearing face in slidable engagement with said swash plate and having acentral projection seating for angular adjustment in said socket, and an opening in said shoe for connecting said passage to said bearing face, said bearing face being formed to maintain a lubricating pressure film area to balance substantially the mechanical reaction tothe pressure in said cylinder.

1l. In a hydraulic pump, in combination, a pump body having a cylinder, a piston reciprocable in said cylinder, an inclined swash-plate l operatively engaging the outer end o f said cylinder, means for effecting relative rotation betweenV said body and said swash plate, valve means for admitting fluid to said cylinder and deliveringA pressure iluid therefrom respectively during the intake and delivery strokes of said piston, said piston being formed with a bearing socket in the outer end and with a longitudinal passage opening from said cylinder to said socket. a. shoe having a flat bearing face in slidable engagement tion, a casing having a wall with inlet passagev means and pressure delivery passage means, an y external boss integral with said wall and formed with a bore opening to the interior of said casing, y

a cylindrical plug tightly fitted in said bore and having an inner end flange engaging the inside of said wall, spline means for locating said plug angularly of said bore, the inner end of said plug defining a flat stationary valve face with arcuate intake and delivery ports inl communication..`

said ports, a drive shaft in said casing and journaled at one end in said last mentioned bore, a.

pump body xed to'said shaft and having a. plurality of parallel pump cylinders annularly arranged about said shaft, a valve face on one end of said body having ports opening respectively to the closed ends of said cylinders, and contacting with saidstationary valve :face for movement of said cylinder ports successively across said intake 'and delivery ports, a lplurality of pistons recipro- 

